Here is the full list of all 16 Sole achievements.
Illuminated the tunnels and chambers of an abandoned cave
Explored the ruins of a beautiful garden and a great library
Skimmed down a river of rushing rapids
Unlocked the secrets of a sprawling city
Illuminated a forgotten world once lost to darkness
Found all the ancient letters around the cave
Found all the ancient letters around Mountain City
Found all the ancient letters in the river
Found all the ancient letters around the flooded city
Found all the ancient letters throughout the lighthouse
Unlocked the entire secret alphabet
Went behind the waterfall inside the cave
Regrew all the dead trees across Mountain City
Flew through all three hoops in the river
Rode the massive elevator in the city
Collected all the charges across the valley sequence